Estimation of Dietary Metabolizable Energy Requirement of Growing Japanese Quail Using Broken Line Regression

A dose-response experiment with seven dietary energy levels (2500, 2650, 2800, 2950, 3100, 3250 and 3400 kcal of MEn/Kg) was implemented to study the effects of dietary energy level on growth performance and carcass characteristics of Japanese quails from 2 to 5 weeks of age. Three hundred and thirty-six 14-day-old Japanese quails were randomly divided into 7 dietary treatments, containing six replicates with eight males and females per each, and the birds were grown up to 5 weeks of age. At 35 d of age, weight gain, feed intake and feed conversion ratio (FCR) of quails from each pen were measured or calculated, and one quail (male one) that had similar body weight to the average of the replication weight was selected and slaughtered to evaluate the yields of carcass parts. The results showed that with an increase in dietary MEn levels feed intake, crude protein intake, FCR and crude protein intake:gain (g/g) of quails decreased significantly (P < 0.05). The highest and the lowest dietary MEn levels resulted in a decrease in body weight gain and metabolizable energy intake (kcal/b). The highest rate of weight gain belonged to moderate dietary energy levels (2800 and 2950 kcal/kg). The results of the experiment revealed that metabolizable energy intake to weight gain, as well as some carcass characteristics such as edible carcass, thighs and breast percentages and giblets (liver, heart and gizzard percentages), were not affected by different dietary energy levels. With increasing dietary energy from 2500 to 2950 kcal MEn/Kg, the weight gain of quail increased and above 2950 kcal/Kg decreased significantly (p=0.0058). Based on broken line regression analysis, between two and four weeks of age, the metabolizable energy requirement of growing quails was 2831 and 2799 Kcal/kg for optimal weight gain and FCR, respectively, when protein level in the diet was 24 percent.